Automatic fuel injector for internal combustion engines



C. NAPOL] 7 May 3, 1960 AUTOMATIC FUEL INJECTOR FOR INTERNAL COMBUSTION ENGINES Filed Dec. 10, 1956 b 3 .w 1 .m 7 H 6 Q N Fig.7

INVENTOR. Car/o Ncz o/L' ATTOKN E55 Unie rates tent AUTOMATIC FUEL INJECTOR FOR INTERNAL v COMBUSTION ENGINES Carlo Napoli, Naples, Italy Application December 10, 1956, Serial No. 627,425

Claims priority, application Italy December 10, 1955 4 Claiim. (Cl. 239-87) This invention relates to a fuel injector and refers more particularly to an automatic fuel injector for internal combustion engines.

In modern automotive engineering there is a definite and increasing trend toward the adoption of internal combustion engines having fuel injection systems, whereby liquid fuels are injected into the combustion chamber when the combustion air is at a desired level of compression. Consequently, the compression can be large enough to ensure a high degree of efiiciency without in curring the danger of premature ignition present in engines fed with carbureted mixtures.

Fuel injection, however, requires complicated and delicate assemblies that are difiicult to manufacture and costly to maintain. These factors limit the adoption of fuel injection systems. Moreover, the injection pump must be driven by the engine which involves problems connected with the proper timing and flow of fuel from the pump to each injector. At high pressures, the injectors are apt to leak and, consequently, are difficul-t to repair.

An object of the present invention is to provide a self-contained injector which ensures perfect atomization of the fuel inside the cylinder, regardless of the pressure therein, without requiring an injection pump and enginedriven elements.

Another object of the present invention is to provide greater simplification and saving in the cost of manufacturing the device.

Still another object is to provide a considerable reduction in the bulk and Weight of the injector of the present invention.

Other objects of the present invention will become apparent during the course of the following specification.

In the attainment of the aforesaid and other objectives, the inventive concept of the present invention may be realized through the provision of an automatic fuel injector which may be used inside a cylinder chamber without requiring an injection pump or other enginedriven element in order for it to perform completely and to atomize the fuel efiiciently therein.

An outer shell may be provided with a series of concentrically disposed small cylinders and pistons slidably and sealably disposed within each other. A further series of similarly disposed smaller connections, each cooperating with one another may likewise be provided to move axially along the cylindrical prolongation of the respective cylinder or piston depending upon the position of each stroke. Radial splines may be fixed to a suitable cylinder for engaging the grooves of a rack, so that the height of the central piston may be varied during the injection of fuel with each stroke.

A fuller understanding of the present invention may be had by referring to the following description taken in conjunction with the accompanying drawings, showing by way of example, a preferred embodiment of the inventive idea.

In the drawing:

Figure 1 is an axial cross-section of the injector.

Fig. 2 is an enlarged perspective view of the pin and nozzle.

Figure 3 is a cross-section of an alternate arrangement of the injector for advancing the injector timing.

Figure 4 is a sectional view showing a portion of the injector illustrated in Fig. l.

Referring now to the drawing in greater detail, wherein like reference numerals indicate like parts, the injector of the present invention is comprised of an outer cylindrical coaxial body or shell 1 provided with a shoulderla and to which is connected another outer cylindrical coaxial body 2 by means of a threaded portion 3. A block 4 is connected to the opposite end of body 2 by means of a bushing 5 illustrated in Figure 1.

A main spring-loaded piston 7 provided with a piston ring 7a and fitted with sealing rings 8 is disposed slidably inside of cylinder 1. Two threaded end portions 7b and 70 having threads of the same pitch are screwed onto one end of an intermediate cylinder 9. The opposite end of hollow cylinder 9 extends upwardly and outside of the threaded end portion 7b. A bushing 10 provided with internal threads secures a tapered atomizer cap or nozzle 11 to one end of the threaded end portion 7c.

Intermediate threaded portions 7b and 7c, cylinder 9 is provided with ports 9a, which are passageways for fuel flowing from the interior'of cylinder 9 to a circular inner cavity 13. r l

The portion 9b of cylinder 9, which extends above the threaded portion 7b is greater in cross-section than threaded portion 7b. Cylinder 9 is provided with ports 25 in its side walls, and which are disposed above portion 9b.

A central piston 15 having a head 15b and a threaded portion is disposed inside cylinder 9. A flange 18 is disposed intermediate the head 15b and threaded POI? tion 150 upon which rests a washer 20 followed by one end of a spiral spring 19. The other end of the spring 19 rests against a bushing 21 which is coaxially and ex ternally disposed in relation with the stem 15a slidably disposed inside the cylinder 9b.

The bushing 21 carries two radial pins 22, the external ends of which project outside of bushing 21 and extend into the ports 25. 'The internal ends of bushing 21 fit into two parallel spiral slots 24 and 24a disposed in the outer wall surfaces of piston 15a. When the piston 15 slides upwardly inside the bushing 21, it is forced to undergo angular movement by the pins 22 with respect to cylinder 9'9b.

I The piston 15 has an inner axial bore 27 which extends over its entire length. A diametrieal opening 28 communicates with ports 9a, and the inner cavity 13. Head 15b of the piston 15 is provided with an axial slot 29 of square cross-section into which fits a correspondingly shaped stem 30 ofequal length. 1 t

Figure 2 represents an enlarged perspective view of the tapered pin 31, showing its tapered part out into four sections. In the inactive position, the four sections cover the corresponding nozzle holes of the atomizer cap 11. When the pin 31 is rotated by piston 15, the four sections uncover the holes 11a of the cap 11, and an atomized jet of fuel is released from the nozzle on account of the heavy pressure existing in the inner lower part of cylinder 9. Normally in the inactive position, pin 31 does not leave its seat, since the base of the taper is larger than the inner diameter of cylinder 9. f

The adjustable spring 19, positioned between washers 20 and bushing 21, pushes the bushing 21 against the lower end 33!) of tube 33. External threads 33a screw the tube 33 firmly into a hollow cylinder 34, which is fitted externally over its entire length with splines 34a ofsquare compression chamber.

- to maintain piston 7 in the rest position shown in Figure 1, while the upper part of the spring 39 tends to push the sleeve 37 against a washer 40 disposed adjacent the block 4. Block 4 carries internally disposed long-pitched' A sleeve 37 is fitted upon the splines 34a.

V V 4 gether with piston 15, thereby causing the position of head b'to changeinside cylinder 9.

The adjustment of the injection advancement is elfected by varying the tension of spring 39. This is done by moving the rack 36, which rotates the cylinder 34 and forces the sleeve 37 to move axially on the long-pitched threads 38.

' I When the raclg 45 passes through a slot tangential to the inner surface of block 4 and engages the splining of bushing 42, the bushing 42 will move axially by way of its long-pitched threads 41, thereby entraining tube 33 together with cylinder 34 without rotating them.

threads 41 which accommodate a bushing 42-provided' with axial splines on its outer surface. One end ofbushing 42 separated by 'a washer 42 rests upon one end of cylinder 34. Bushing 42 bears against cylinder 34' by means of an inner shoulder 42a which engages a shoulder of tube 33 screwed to cylinder 34.

A rack 45 is disposed parallel to rack 36 and meshes with the splining of bushing 42. 1

A fuel feed tube 47 is positioned'inside of tube 33 an piston 15, while the upper end of tube 47 slides through a seal 48 contained in a tube 49.

The tube 49 carries a flange 49a, which is screwed into place by a bushing 50 and secured to the externally disposed threads of block 4. A fuel line 27ais fastened by means of a screw connector 51 to one-end of the bushing 50.

1 The-operation of the injector described above is as follows: i p

The device is shown in the rest position in Figurel. No pressure exists in the combustion chamber or pre chamber. When the air pressure has risen'sufiiciently for piston 7 to overcome the resistance. of spring 39, piston 7 and cylinder 9 begin to rise, gradually closing the ports 9a through which the fuel fiowsinto the inner cavity chamber 13. v a

The fuel is compressed to the desiredinjection pressure a level when. the ports 9a are totally closed to the circumferential inner cavity 13. The compression of the fuel and closure of the ports 9a beginwhen the piston head 15b enters the terminal part of cylinder 9. As soon as the pressure is reached, the spring 19, adjusted to; the pressure, permits piston 15 to recede backwardly together with the movement of cylinder 9. The stem 15a of piston 15 is then forced against bushing 21, thdposition of which depends upon the position of bushing 42 and the position of rack 45. 7

As the piston 15 slides through bushing 21, the action and location of pins 22 cause the piston 15 and stems 7 Tube 33 is connected in its axial movements with stem 15a by means of an inner shoulder 33b disposed on the lower edge of the tube 33. ,The movement of shoulder 33b is-restricted by stem 15a, since it is bound between bushing 21 and the head of tube 47. Therefore, the transverse'movement'of rack 45 produces only axial sliding of piston 15 into cylinder 9. The cylinder 34 and tube 33 do not interfere with the movement of bushing 1 37. For the samereason, by moving rack 36, the'movecommunicates with and connectsiwith'the lower end of v ment of cylinder 34, whatever its vertical position, causes sleeve 37 to revolve and to move along the threadedportions 38, thereby changingthe tension of the spring 39 without causing any movement of bushing 42 and piston fWhen the compression level in the chamber or prechamber. is sufiicient to allow the lifting of piston 7, the movement of spring 39 is retarded if its tension is increased, and, consequently, the frequency of operation of V the injector-yas'desciibed above, is also diminished.

One change with respect to the injector, as described I above, may be had by making the spring 39 perform only the function .of pulling the piston 7 towards thefrest position illustrated in Figure 1. The adjustment of the injection advancement is obtained by the back pressure produced inside the injector body to retard the travel of piston 7. a Q

In accordance with this arrangement, the change above-mentioned is illustrated inligure 3, wherein like reference numerals indicate like parts. Calibrated ducts 55 are provided in the shell wall 1a and communicate with ducts 56 in the body of the piston 7. During the compression stroke, part of the compressed airis bled from'the cylinder chamber to theback face of piston 7', which closes the air passage or communication'as soon as piston 7 moves forward sufiiciently enough to'seal off 15-1511 to rotate ;,the taper pin 31, which'opens the V nozzlea-tomizing holes 11a. During injection the pressure of the fuel remains constant as piston 15 advances into'cylinder '9. As soon as spring19 is distended, fuel injection ceases, since the entire length of piston 15 has advanced completely, The stem 15a moves out of the bushing 21 the same distance as it has entered into the bushing 21, thereby causing the stern 15a to rotate in the opposite direction to close the nozzle atomizer holes.

The extent to which the piston 15 enters cylinder 9 determines the volume of injection which varies the.

length of the stroke ,of thepiston extending into the In eflFect, piston 7 together with cylinder 9 generally travels the same distance. Consequently, the stroke of piston 15, which extends into the combustion chamber, depends upon thedistance that head 15b enters the combustion chamber. Thus, the quantity of fuel injected is controlled by, varying the operating 7 stroke of piston '15 in the following manner: Byrmovin'g the rack 45, the ring 42 rotates; by. screwing the threads. '41 of block 4, the cylinder 34 movesjaxially without rotating it; thus, cylinder 34 carrieswith it tube 33 to ducts 55.from ducts 56.. Thus, the value of the backpressure which retards the stroke of piston 7 is 'controlled by the engine speed. 1 An increase in speed will decrease the volume of airwhich is bled to'provide back-pressure. Consequently, the value of the'backpressure will be lower and the angle of greater, and vice versa..

It is'to be understood'that the present invention istnot restricted to the embodiments described 'hereinabove,

since it is possible to produce still other embodiments without'departing from the inventive concept herein disclosed, and it is desired, therefore, that only such limitations be imposed on the appended claims as are herein described. 7

metrical opening communicating with said inner bore,

and an axial slot of prismatic section at one end of said piston, a nozzle having a plurality of holes removably carried by said main spring-loaded piston, aistem extending into said second-mentioned axial bore and apin" advancement integral with said stem and divided into several sections adapted to open and close said nozzle holes, a bushing mounted coaxially on said central piston, radial pins carried by said bushing and engaging said port of said intermediate cylinder and said spiral grooves of said central piston, an adjustable spiral spring disposed coaxially on said central piston intermediate said bushing and said flange, and a fuel feed tube carried by said central piston and communicating with said inner bore, said intermediate cylinder having lower ports, the walls of said main piston and said intermediate cylinder being spaced to form an inner cavity communicating with said lower ports.

2. A fuel injector for internal combustion engines in accordance with claim 1, comprising a spring coaxially disposed on said main piston for loading said main spring, and tension varying means, said tension varying means comprising a rack, a sleeve and a plurality of splines carried by said sleeve and meshing with said rack, said sleeve having a plurality of externally disposed threads meshing with internally disposed threads of said outer shell.

3. A fuel injector for internal combustion engines in accordance with claim 1 wherein the quantity of fuel injected at each stroke is controlled by a device, said device comprising a rack, another bushing, and a plurality of splines fixed to the outer surface of the lastnientioned bushing.

4. A fuel injector for internal combustion engines in accordance with claim '1 wherein the lower part of said outer shell is provided with calibrated ducts, said ducts being adapted to engage other ducts in said main springloaded piston for bleeding compressed air to the back face surface of said main piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,995,459 Olsen Mar. 26, 1935 FOREIGN PATENTS 628,016 Great Britain Aug. 19, 1948 

